During 1979, we hope to complete our genetic analysis of the phosphorus control system of Neurospora, especially the analysis of gene balance and dosage of control genes on repressible or constitutive synthesis of alkaline phosphatase. We will continue in our work on the molecular basis of control in this system, with particular attention to cloning of the structural and control genes. We will attempt to verify candidates for cloned pho-2 gene by using nick-translated cloned material to probe genomic blot-throughs of suitable restriction digests of genome DNA. These genome DNA samples will be isolated from Neurospora pho-2 mutants containing translocations that appear to cut into the pho-2 gene, and from Normal Sequence controls. We will continue our study of the organization and control of the ribosomal genes of Neurospora. We will examine whether different 5S rDNA clones we have isolated are embedded in different sorts of chromosomal environments, as they appear to be from probing of restriction digests of genomic DNA. (This will be done in collaboration with Mr. Eric Selker and Dr. Charles Yanofsky). The control of synthesis of ribosomal RNA by phosphorus starvation, sulfur starvation, etc., will be studied, using covalently-bound rDNA drivers which we have prepared. In addition, we will try to clone the first and last of the main rDNA repeat units of the roughly 185 tandem units which presumably are located in the nucleolus organizer region.